larryqian wrote: > Dear All, > > During a data query or any of the data operation, if the coresponding > Region Server crashes, will the query continue to work on another Region > Server? Or the query fails and return error to Application? >
Depends. Recovery from crash may take some time; a second or two and even up to minutes if the crashed server was carrying catalog table regions. Client may time out in the meantime. If the region the query goes against comes back on line promptly, then client will return query results as though the crash had not happend. > If a free Region Server crashes, the master will find and reschdule the > assigned task after 1 hearbeat, right? > Its all configurable but no, not after one heartbeat. Heartbeats are every couple of seconds. <property> <name>hbase.regionserver.msginterval</name> <value>3000</value> <description>Interval between messages from the RegionServer to HMaster in milliseconds. Default is 3 seconds. </description> </property> Master will consider regionserver dead only after the regionservers' lease expires in the master. This is the below configuration: <property> <name>hbase.master.lease.period</name> <value>120000</value> <description>HMaster server lease period in milliseconds. Default is 120 seconds. Region servers must report in within this period else they are considered dead. On loaded cluster, may need to up this period.</description> </property> St.Ack
